Notorious hacking group Lizard Squad has claimed responsibility for a DDoS attack on a Blizzard datacenter, resulting in all Battle.net powered titles going offline in the US and Europe, reports IGN.

Though games are now coming back online, Lizard Squad claimed it managed to take World of Warcraft, Diablo 3, StarCraft 2 and Hearthstone offline.

Members of the group also claimed to have gained access to some Blizzard emails.

No reason for the attack has been given, though there is speculation it is retaliation to Blizzard issuing a cease-and-desist notice to popular pirate World of Warcraft server, Nostalrius.

Blizzard has acknowledged the attack and says games should begin coming back online.

"It looks like we experienced a potential DDoS on one of our datacenters. Initial impact appears to have ended and our engineers put up some buffers to resolve the issue, and realms should start recovering," explained a Blizzard engineer. "We're continuing to monitor and work on mitigating the impact. Apologies for the inconvenience, and we'll be sure to provide updates as they continue to come in."